updated local_binary_pattern documentation

The reference link was divided into two lines thereby linking to only half the url
Fixed ellipse symmetry and added some tests.
Added float conversions for python2.x
Add ndim checks in filter.edges
Updated CONTRIBUTORS.txt
Merge pull request #1156 from alexeyum/ellipse-symmetry

Ellipse symmetry
Merge pull request #1155 from atemysemicolon/master

updated local_binary_pattern documentation
Implement new assert_nD utility function
Merge pull request #1159 from blink1073/check-ndims-in-edges

Add ndim checks in filter.edges